MILWAUKEE, Feb 26 (Reuters) - A Wisconsin man convicted of sexually assaulting his stepsister while she was held captive and starved for years by their parents in the basement of their house was sentenced on Wednesday to three years in prison, prosecutors said.

Joshua Drabek, 20, was convicted by a Dane County jury on Feb. 21 of first degree sexual assault of a child without great bodily harm, second degree sexual assault of a child and child abuse-intentionally causing harm, according to court records.

Drabek was accused of forcing her to engage in oral sex and trying to have intercourse with her, according to a criminal compliant.

The girl, now 17, was held captive by their parents for six years in the basement of their Madison house, rarely given food and forced to eat off the floor, according to a criminal complaint. She told detectives the couple forced her to use boxes or bags as a toilet and to bathe in a utility sink.

The girl's father, Chad Chritton, 42, and his wife Melinda Drabek-Chritton, 44, who is Drabek's mother, were sentenced to five years in prison each in the case. Chritton also received five years extended supervision.

The couple had told investigators they home-schooled the girl and needed to lock her in the basement because she had mental health issues.

The couple also forced the girl to do chores naked so she could not hide food in her clothing, according to the criminal complaint.

Separately, Drabek was also sentenced on Wednesday in a Dane County Circuit Court to two years in prison for sexually assaulting another girl after pleading guilty in that case in July, assistant district attorney Matthew Moeser said. (Editing by Eric Walsh)